Rotating heat engine



Dec. 8, 1942. w, KARRER ROTATING HEAT ENGINE Filed June 4, 1940 INVENTOR /Verzer Kar/"e2: M

7 ATTORN Y Patented Dec. 8, 1942 ROTATING HEAT ENGINE Werner Karrer, Zurich, Switzerland, assignor to Maschinenfabrik Oerlikon, Oerlikon, Switzerland, a corporation of Switzerland Application June 4, 1940, Serial No. 338,690 In Switzerland June 13, 1939 8 Claims.

The efficiency of heat engines is known to increase with the temperature, and it is known that in particular gas or hot-air turbines can be operated economically only at working temperatures of 500 to 600 C. The higher the temperatures that may be employed the more economical are such plants.

In order to be employed at high temperatures in machines, materials must fulfill two important conditions. In the rst place they must be sufficiently strong to take up the stresses occurring in operation (e. g., in blades and wheel discs); in the second place, they must be free from scale, that is to say that at the contact surfaces between the material and the hot working substance no oxidation must take place which would lead to the flaking of the material.

The employment of any desirable high temperatures is prevented today by the properties of the materials, as the strength of the latter is not sufcient at temperatures over 600 C. (hot strong materials), while as to freedom from scale there are available today materials which give satisfaction up to 1000 C. and over, however only if they need not take up any stresses (heat resisting materials).

Now, a commonly known expedient is to cool the stressed materials, especially the blades of', turbines, with circulating water, thus keeping ,f

their temperatures within admissible limits. However, the cooling of the blades, especially the moving blades, involves several disadvantages. On the one hand it is diicult to seal the channels of the water supply, then again a great drop of temperature occurs Within the stressed parts for a short distance when water is the coolant, which is disadvantageous for the stressed parts, and finally the extent of the cooling is restricted by the great amount of heat to be eliminated which may be a disadvantageous in` uence on the efiiciency of the whole plant.

According to the present invention the materials subjected to mechanical stresses are covered with a layer of a heat-insulating material. In this manner the main temperature drop on the hot side is to be transferred outside the stressed materials, which then exhibit a fairly constant temperature over their whole extent and can therefore now be stressed like ordinary materials. Apart from the advantage offered by the elimination of complicated cooling arrangements it is possible to reduce heat losses to a minimum by providing for generous dimensions for the heat-insulating layers. The natural heat removal by way of shaft and bearings may suffice to maintain the temperature of said protected parts within admissible limits. Elimination of heat to the surroundings may be improved by the provision of ribs. Finally, more remote parts that can be reached more readily by a flow of coolant than moving and distributing apparatus, e. g., shaft or wheel, may be provided with an artificial cooling system. Today it is possible to apply a heat-insulating layer to the vital parts of the machine, as heat-resisting protective substances are available for their protection.substances which can stand the temperature of the hot working medium and can sustain themselves. It is expedient to transform the tensile stresses of said protective coverings as much as possible into compressive stresses. Thus the moving blades are designed for example with head bands which take up the tensile stress of the heat-insulating and the heatresisting protective substance and transform it into compressive stresses.

The decrease of the temperature of metal parts by means of insulation may be effected in the rotating and the stationary parts of the turbine. At certain points, especially on the stator, the insulating protection by means of heat-resisting metal covers may be omitted. The heat-insulating substance may be sprayed on the supporting or the protective metal, or inserted between the two or forced in. The protective material may also be applied by means of a spraying process.

The annexed drawing shows diagrammatical examples of embodiment of the subject matter of the invention. Fig. 1 shows a rotor with blade in section, Fig. 2 a section of a moving blade with view on the head band, Fig. 3 two moving blades in section with view on the intermediate covering piece on the wheel rim, Fig. 4 the longitudinal section of a moving blade, Fig. 5 a section of a distributor, and Fig. 6 a section of a guide blade.

In Fig. 1, I is the shaft, 2 is the rotating Wheel, 3 a moving blade. The blade 3 may be made of either hot-strong metal capable of resisting temperatures of about 600 degrees centigrade or of ordinary metal. The foot 5 of the blade 3 is inserted in the rim l0 of the rotating wheel 2. Blade and wheel may also be integral. The head band 6 is made in one piece with the blade 3. Wheel and blade are covered with a heat-insulating layer 'l.` This layer may be made of solid material placed over the supporting blade and wheel or may be sprayed on the latter. If the insulating layer 'I can be durably applied, it will be sufficient without any additional protection. However, in Fig. 1 Water cooling of the wheel is provided for in the hub 4 to promote the removal of the heat.

In order to protect the insulating layer against the effects of stresses, a protective covering of metal capable of resisting temperatures of about 1000 degrees centigrade and over is placed over the layer l, consisting of the parts I3, I4, 9, I2 and II, which consist of said heat-resisting metal. As indicated in Fig. 1, the edges of the individual parts of the protective covering may be welded together. It is advisable to leave a clearance between the protective covering 9 and the wheel rim I0, to allow the former to expand freely; it is put under compressive stress by the centrifugal force. The centrifugal forces of the protective coverings 3 and II are taken up by the head band 6 of the cold supporting blade 3. The two protective coverings I3 can expand freely in a downward direction; it is best to construct them as discs of the same strength.

Protection of the heat insulation on the outer wheel rim is effected by the covering parts I4 (Fig. 3) placed between the blades 3, which on both sides are welded to the covering discs I3.

In this manner the supporting wheel 2 and the supporting blade 3 are protected by means of heat insulation 1 and the latter by means of said heat resistant metal, against the impulsive and centrifugal forces, while on the contrary the centrifugal forces of the insulation and protective material are largely taken up again by the cold supporting material 2 and 3. Such a structure may therefore be subjected to substantially higher working substance temperatures than an ordinary hot-strong blade, without paying the price of a complicated cooling water supply or great heat losses.

The protective covering I I may also be omitted. As the small unprotected face I2 of the blade does not receive any impacts from the working substance, the insulation is less stressed at this point.

Finally, not only the protective covering, but also the insulation may be omitted at the faces, as the small face of the supporting blade can take up only little heat, which in the presence of sufcient removal maintains the temperature at the face at admissible values.

Figs. 5 and 6 show a distributor and a guide blade respectively, which are protected on the same principles. I5 is the blade made of hot strong or ordinary material, I6 is the insulation and I1 the protective covering. I8 and I9 are the protective plates of the guide disc consistlng of heat resistant material; they enclose the insulation 20, which protects the disc 2I.

The structural embodiments may be of any convenient kind; the protective coverings may be retained for example at the foot between the blade and the wheel.

Having thus described my invention, I claim:

1. A rotating heat engine having a turbine wheel comprising a, metallic disk provided with metallic vanes, said disk and vanes being coated with a layer of heat insulating material, and said layer of insulating material being coated with a layer oi' metal having a resistance to disintegration resulting from heat, which resistance is higher than that of the metal of said disk and vanes.

2. A rotating heat engine having a turbine wheel comprising a metallic disk provided with metallic vanes, said vanes being coated with a layer of heat insulating material, and said layer of insulating material being coated with a layer of metal having a resistance to disintegration resulting from heat, which resistance is higher than that of said metal of said vanes.

3. A rotating heat engine having a turbine wheel comprising a metallic disk provided with metallic vanes, said disk being coated with a layer of heat insulating material, and said layer of insulating material being coated with a layer of metal having a resistance to disintegration resulting from heat, which resistance is higher than that of said metal of said disk.

4. A rotating heat engine having a turbine wheel comprising a metallic frame provided with metallic vanes, said frame and vanes being coated with a layer of heat insulating material, said layer of insulating material being coated with a layer of metal having a resistance to disintegration resulting from heat, which resistance is higher than that of the metal of said frame and vanes, and said metal of said higher heat resistance being held to said layer of insulating material by adhesion.

5. A rotating heat engine having a turbine wheel comprising a metallic frame provided with metallic vanes, said vanes being coated with a layer of heat insulating material, said layer of insulating material being coated with a layer of metal having a resistance to disintegration resulting from heat, which resistance is higher than that of said metal of said vanes, and said metal of said higher heat resistance being held to said layer of insulating material by adhesion.

6. A rotating heat engine having a turbine wheel comprising a metallic drum provided with metallic vanes, said drum being coated with a layer of heat insulating material, said layer of insulating material being coated with a layer of metal having a resistance to disintegration resulting from heat, which resistance is higher than that of said metal of said drum, and said metal of said higher heat resistance being held to said layer of insulating material by adhesion.

7. A rotating heat engine comprising a turbine wheel including a metallic drum with metallic vanes, said vanes being coated with a layer of heat insulating material, said layer of insulating material being coated with a layer of metal having a resistance to disintegration resulting from heat, which resistance is higher than that of said metal of said vanes, and the terminal of each of said vanes having a rim projecting over the terminals of both of said layers.

8. A rotating heat engine including a series of metallic vanes, said vanes being coated with a layer of heat insulating material, and said layer of heat insulating material being coated with a layer of metal having a resistance to disintegration resulting from heat, which resistance is higher than that of the metal comprising said vanes.

WERNER. KARRER.

.. n v.r Y, l 

